The washers only offer a small amount of preload just enough to keep the guts from rattling around.
There is a Torsen called a Type 2 R that uses clutch packs to provide enough preload to prevent the diff from turning into an open on wheel lift.

The T2R is used in the s2000 and based on indirect evidence I'm willing to bet the MSM Miata has one as well.

My car's been in the shop since 9 this morning. I rode my motorbike by on my way to work around 12:30 and it was parked in the same spot but the hood was open. Obviously ogling my turbo and not working on car :p Hopefully I can get it back tomorrow, and hopefully it doesn't grenade on me.

I'm doing this all for MT btw. :p

I will have results in a few weeks too. I am going to be running mine at a hill climb pretty much right out of the box. With hopefully 300whp +-.

Washers control noise, not preload.

Bad news so far. The surface that the ring mounts on was not flat, and was out 10,000. They are sending it to a machine shop right now to get it made true. It was causing the ring to rotate out of the pinion.

Oh oh

This is not good news, you mean .010", when you say 10'000 right?

Yes. This thing better work well once it gets machined.

Good thing that was checked, otherwise you would have been finding out it wasn't correct the hard way.

How did they find this out? Just by chance or is it something they check?

They put it in with bearings any everything, and were checking the rotation and noticed the pinion kept coming off the ring. They tried a few things and then checked the measurements of the diff and found out it was out of whack.

Can you circle or show the part that was actually not flat? I'm having a hard time figuring out which piece needs to be perfectly flat.

It's the big flat ring around the diff housing that the ring gear sits on.

It's fairly simple to detect, when you're setting the back lash between the pinion and ring gear, if the ring gear is not running true, it'll be loose on one side and tight on the other. What's OEM spec? Couple .001"? .010" isn't a lot, but definitely towards the high side of gear mesh tolerance, and I'm only used to straight or helical gears, not ring/pinion.

Backlash is supposed to be within plus or minus .002 IIRC, so the .010 out means it would never be within spec.

Success! Shop just called to say that it's installed and working great. I will pick it up around noon.

Sweet, are they going to give you a spec sheet with the install info/measurements?

This sounds interesting. Not a replacement for the Type II in the MSM, but it would be a damn nice budget 3.6/LSD in an open diff for about the price of a stock 4:10/3.9 lsd.

BTW, someone mentioned they think the MSM is a torsen type II, which it is. The S2k actually uses the Mazda 7" ring gear and the mazda uses the S2k diff. A guy with an MSM replaced his diff with an OSgiken, found this out.

Isnt the Type I better for accel locking, and Type II for decel?


but the Type II is quiter and smoother in operation?

I could have sworn the msm diff is a torque sensing unit made by bosch that is something like a hybrid type two (that is also sprung). Is that not correct? If not is there a link for msm diff knowledge?

nothing special about the MSM torsen, same as S2K. there was some POS Fuji Super LSD in whatever '03 miata...